The sap of maple trees forms the basis of maple-based products, including maple syrup, maple sugar and maple confection products. Maple syrup is obtained by the concentration of maple sap, a low solids (low sugar) solution obtained from the maple tree, to a solids content of 66 percent (66 degrees Brix). The production of maple syrup and related products is highly regulated in Canada and the United States, such that all additives are prohibited. As a result, maple producers cannot simply use additives such as stabilizers if they wish to label their product as a “pure maple-based product” or as “ pure maple syrup”.
To produce maple syrup, the sap from maple tree is concentrated to 66 degrees Brix (at 68 degrees Fahrenheit; 20 degrees Celsius) to be considered as “pure maple syrup” by U.S. and Canadian law. About 40 liters of maple sap are needed to make 1 liter of maple syrup. During the evaporation process, the sap is heated which induces chemical changes that give maple syrup its characteristic color and flavor. These chemical changes include non-enzymatic browning and caramelization reactions (Edson, 1910; Hayward and Pederson, 1946).
Concentration can be achieved through simple boiling in an open kettle or using more advanced evaporation techniques such as vacuum pan evaporators and rising film or falling film evaporators. Various other methods are known for concentrating maple sap. For example, U.S. Pat. No. 5,389,209 to Paquette discloses a method of boiling the sap under normal pressure, then heating the sap to below boiling temperature and using an air circulating column to further evaporate the water. Reverse osmosis can be used to pre-concentrate the sap to about 20-25 degrees Brix. An alternate concentration step, which involves the addition of heat, must be used to complete the concentration to 66 degrees Brix such that the characteristic maple flavor is created (North American Maple Producers Manual, Bulletin 856, chapter 7).
Concentrating to a higher level (over 67.5 degrees Brix) will result in crystallization of the sucrose, the main sugar found in maple sap, within the container while in storage. Conversely, a maple syrup of lower Brix (under 64.5 degrees Brix) would spoil (ferment) while in storage. Crystallization occurs because the main sugar in maple syrup is sucrose (90-100 percent), with the rest being glucose (0 to 10 percent) (North American Maple Syrup Producers Manual, Bulletin 856, Appendix 2).
It is the crystallization behavior of maple syrup at higher concentration that allows for the production of other maple-based products such as maple sugar. These products are obtained by concentrating maple syrup past 66 degrees Brix. At these elevated Brix levels, a supersaturated sucrose solution is made. Therefore, if this solution is cooled, crystallization will occur. Depending on the rate of cooling and/or whether agitation is present during the cooling process, characteristic maple-based products are obtained. Slow cooling without agitation results in crystals that are very large, often termed “rock candy”. More rapid cooling, but again without agitation, will result in smaller crystals but the product has a very gritty mouthfeel. When a highly supersaturated maple syrup solution (85 to 90 degrees Brix) is cooled very rapidly without agitation, a non-crystalline glass-like solid is obtained (North American Maple Syrup Producers Manual, Bulletin 856, chapter 9).
Conversely, if a supersaturated (84 to 85 degrees Brix; or 12 to 13 degrees Celsius above the boiling point of water) maple syrup solution is cooled rapidly with high-speed agitation, very small crystals are obtained with the resultant product being paste-like in consistency and is spreadable. This product is known as maple butter or maple cream. Currently there is no pure maple-based product with this paste-like consistency that is shelf stable.
Crystallization of the sugars found in maple syrup is random and occurs spontaneously at higher Brix levels. Because the crystallization behavior of concentrated maple sap is difficult to control, only a select few products have been developed. Additionally, at a concentration of 66 degrees Brix, maple syrup may be too runny (thin) to be used in an application such as a honey like spread. Currently, there is no natural or pure maple-based product which has the consistency and/or appearance similar to that of clear honey.
Clear honey is a transparent high viscosity 3.9 Pascal seconds sugar syrup with a moisture content of 17 to 19 percent (81 to 83 degrees Brix solids) (Rheological Methods in Food Process Engineering, Steffe, J. F. 1996, pp 82, 26 and 367). This material remains in a clear state, without crystallization for extended periods of time. The main sugar components in honey are the monosaccharides glucose and fructose. These sugars are present in maple syrup in small amounts.
As previously described, a more viscous solution similar to that of clear honey, having a unique maple flavor, is attainable by further concentrating maple syrup to a higher Brix level (81 to 82 degrees Brix for example). However, when this supersaturated solution is cooled, crystallization occurs rapidly such that the clear viscous solution would not be preserved. This occurs because the main sugar in maple syrup is the disaccharide sucrose, which crystallizes much more readily than glucose and fructose.
Pure glucose and fructose blends are available commercially and are known as invert sugars. It is known to use invert sugar (glucose/fructose) when making artificial maple-based products. It is also known that invert sugar tends to retard crystallization in maple-based products. However, simply adding invert sugar can lead to loss of natural maple flavor. Additionally, the resultant maple- based product may no longer be labeled or considered as pure under the Canadian and U.S. legal standards.
Invert sugars have also been used in making imitation maple syrup or syrup substitutes. U.S. Pat. No. 3,878,306 to Garstick discloses an imitation maple syrup made from various sugars and artificial flavorings. U.S. Pat. No. 4,938,989 to Steeves and McKelvey provides a maple syrup substitute which contains maple syrup, maple flavor, fructose and glucose and white sugar. Again, these products could not be considered pure maple-based products.
It is known in the art that sucrose can be cleaved into its constituent sugars, glucose and fructose by use of an acid such as L-tartaric acid (cream of tartar). However, the use of organic acids leads to products that have very poor flavor profiles and unacceptable appearances. A further challenge is that the acid would have to be removed, after it has cleaved the sucrose. This step would also remove important flavor components.
The difficulty in making stable high viscosity maple syrups extends to other maple-based products. For example, maple butter (also called maple cream or maple spread) separates into two layers if not stored at temperatures below 0 degrees Celsius or 32 degrees Fahrenheit. A dilute syrup layer forms on top and a solid crystalline mass forms underneath. Maple butter is made by heating maple syrup to 11 to 13 degrees Celsius above the boiling point of water (83 to 86 degrees Brix), and cooling rapidly while stirring.
Many viscosity-altering hydrocolloid substances are commonly used in food products, and are known in the art as stabilizing products, or ‘stabilizers’. Two commonly used stabilizers are carageenan and xanthan. Stabilizers are added to prevent phase separation in liquids or solids such as ice cream and peanut butter. However, these stabilizers have not been used to date in maple-based products. Carrageenan is extracted from seaweed, while xanthan is derived from an industrial fermentation of a bacteria.
Accordingly, there is a need for a shelf stable, spreadable, non-crystalline maple syrup product with the consistency of clear honey.
Accordingly, there is also a need for an enzyme treated maple syrup that when added to products increases the shelf stability of the product by preventing the visible crystallization or separation of the product. There is also a need for shelf stable products containing enzyme treated maple syrup.
Accordingly, there is also a need for a spreadable, shelf stable, maple butter with the consistency of churned honey.
Accordingly, there is also a need for a shelf stable, maple butter that is a pure maple-based product.